A DELETION WITHIN THE MURINE WERNER-SYNDROME HELICASE INDUCES SENSITIVITY TO INHIBITORS OF TOPOISOMERASE AND LOSS OF CELLULAR PROLIFERATIVECAPACITY

Werner syndrome (WS) is an autosomal recessive disorder characterized by genomic instability and the premature onset of a number of age-rela ted diseases. The gene responsible for WS encodes a member of the RecQ -like subfamily of DNA helicases, Here we show that its murine homolog ue maps to murine chromosome 8 in a region syntenic with the human WRN gene. We have deleted a segment of this gene and created Wrn-deficien t embryonic stem (ES) cells and WS mice. While displaying reduced embr yonic survival, live-born WS mice otherwise appear normal during their first year of life. Nonetheless, although several DNA repair systems are apparently intact in homozygous WS ES cells, such cells display a higher mutation rate and are significantly more sensitive to topoisome rase inhibitors (especially camptothecin) than are wild-type ES cells. Furthermore, mouse embryo fibroblasts derived from homozygous WS embr yos show premature loss of proliferative capacity. At the molecular le vel, wild-type, but not mutant, WS protein copurifies through a series of centrifugation and chromatography steps with a multiprotein DNA re plication complex.